Frequency-matching system



Aug. 5, 1947. w. R. CARTER 2,425,029

FREQUENCYTMATCHING SYSTEM Filed July 1, 1944 2 Sheets Sheet' l .r ..e Q a 7 MM. mm. m y c j v a R .1. o o o w MAW o 1v I! o O o w u W s 4 V ,fi 5 5 a i R 5 fi 1 N2 \5. on l9 v E $3 w a y w g $7 8/ N J Q s. WP, Li E g 3 A mi El w v 4 x x x L 3% M E a as 5 mi m a 3 Aug! 1947. w. R. CARTER I 2,425,028

FREQUENCY-MATCHING SYSTEM Filed July 1, 1944 2 Sheets-Sheet 2 A 1 5 92 ci 7 9i iii 99 89 79 57 869 89 I 52: Z7 97 j V/Lliiam Carter I We;

Patented Aug. 5, 1947 FREQUEN CY-MATCHIN G SYSTEM William R. Carter, Minneapolis, Minn., assignor to Electric Machinery Manufacturing Company, Minneapolis, Minn.

Application July 1, 1944, Serial No. 543,185

16 Claims.

My invention relates to frequency-matching systems for alternating-current generators and has for an object to provide a system in which the frequency of the generator is maintained within close limits to the frequency of the alternating-current electrical system to which the generator is to be connected.

Another object of the invention resides in providing a frequency-matching device which is highly responsive to variations in frequency.

A still further object of the invention resides providing a frequency-matching device which sensitive and positive in action.

An object of the invention resides in providing a frequency-matching device utilizing a core structure having two balanced magnetic circuits energized from the generator and the electrical system with which the generator is to be connected, and in providing an armature operable through unbalance of the magnetic circuits produced by variations of the frequencies of the generator and electrical system for controlling the speed of the generator to be synchronized to the system.

A feature of the invention resides in energizing said magnetic circuits by means of two electrical circuits, each having a condenser and a winding connected in resonant relationship.

Another object of the invention resides in providing the core structure with two core members having windings thereon energized by the circuits connected to the generator, and the electrical system with which it is to be synchronized and in further providing condensers connected in said electrical circuits in series with said windmgs.

A still further object of the invention resides in providing a frequency-matching system in which a frequency-matching motor is employed for varying the speed of the generator to be synchronized together with driving means adapted to be disconnected from the motor upon synchronization of the generator with the electrical system.

An object of the invention resides in providing a clutch driven by the frequency-matching motor for varying the speed of the generator and in further providing means for disengaging said clutch upon synchronization of the generator with the electrical system.

Other objects of the invention reside in the novel combination and arrangement of parts and in the details of construction hereinafter illustrated and/ or describedn In the drawings:

in is Fig. 1 is a Wiring diagram of a frequencymatching system illustrating an embodiment of my invention.

Fig. 2 is an elevational detail view of the irequency-matching dry mechanism.

Fig. 3 is a plan View of the frequencynnatching device.

Fig. 4 is a cross-sectional view taken on line 44 of Fig. 3.

Fig. 5 is an elevational sectional detail View taken on line 5-5 of Fig. 3 and drawn to a greater scale.

In Fig. 1, I have shown a frequency-matching system in which an alternating-current generator I l of ordinary construction is to be synchronized with an electrical system, a part of which is represented by the line 20 having conductors l2 and 13. The generator H is adapted to be connected to the line 20 by means of a line 39 having conductors l4 and [5, in a manner to be presently more fully described. The generator H is driven by a prime mover I6 which may be an internal combustion engine, a steam engine, a water wheel, an electric motor or the like. In any event, the prime mover I6 is provided with some means for varying the speed thereof which, in the case of an internal combustion engine or a steam engine, might be the throttle or the fuel supply. In the event of a water wheel, the same would be the gate or other means for controlling the pressure or amount of water flowing to the wheel. The present invention includes a reversible electric motor indicated at H which operates to vary such speed-varying device for the prime mover and to change the speed thereof. The electric motor I? operates through a drive means 18 to vary the speed of the prime mover and is actuated by means of a frequency-matching device designated in its entirety by the reference numeral I9. A synchronizing device 2! connects the generator line 30 to the system line 20 through a line switch 22 when the frequencymatching device has brought the generator to synchronous speed. These various parts will now be described in detail.

For the purpose of illustrating the invention, I have shown in Fig. 2 a portion of a governor 23 for an internal combustion engine used as the prime mover Hi. This governor has the usual rotating elements (not shown) which operate the throttle of the engine to increase or decrease the speed, depending upon the position of said rotating elements. A shaft 24 of the governor 23 is turned by the movement of the rotating elements of the governor and, in turn, moves the throttle of the engine to vary the speed of the same. Since the construction of governors for internal combustion engines is well known in the art, the construction of the same has not been shown in detail in this application. The shaft 724 has an arm 25 secured to it which extends upwardly therefrom and by means of which the shaft 24 may be turned independently of the governor actuating mechanism. In the normal operation of the governor, the arm 25 engages a limit screw 51 which is threaded in a lug fill attached to the governor proper. This limit screw is held in adjusted position by means of a lock nut 59. A tension coil spring 6i, attached to the arm 25 and to a part fixed relative to the governor proper, maintains the arm 25 in cngagement with the screw 51. This construction limits the maximum speed of the prime mover: but permits opening of the throttle when the speed of the engine drops.

In the particular construction shown in l and 2, the electric motor illustrated is of the shaded pole type and comprises a core structure 25 having two main poles ill and 23 and auxiliary or shaded poles 29, 2H, 32 and 33. Within these poles, a rotor 34 is mounted for rotation which is supported by a shaft 35. The core structure 25 has a main winding 3% on it which produces flux through the main poles 21 and 23. The auxiliary or shaded poles 29, 3|, 32 and 33 have windings: 3?, 33, 39 and M on them which are adapted to be short-circuited in diagonally disposed pairs to provide shaded poles which control the direction of rotation of the rotor 34. These various windings are connected in a manner to be presently described in detail.

The :notor i! is mounted on a base 42 which is attached to the governor 23. Also mounted on this base is a gear reduction 43 diagrammatically "heated in Fig. 1 by sets of spur gears. It can readily comprehended that any other type of gear reduction may be used in place thereof. This gear reduction has a driven shaft 64 which extends outwardly therefrom and which is driven from the shaft of motor Il' at a greatly reduced speed.

On the shaft M is mounted a clutch 45 which includes a plate 46 securely attached to the shaft 44. This plate constructed of magnetic material such as iron. Cooperating with the plate 46 is a rotatable core member M which has a hub 48 at the center of the same and an annulus 49 at the outer portion of the same. The said hub and annulus have core faces and 52 which lie in a plane and which are disposed in close proximity to the plate 46. A coil 53, wound on the hub 48, serves to energize the core member i"! and to cause the same to be attracted to the plate Mi. When the coil 53 is energized, the clutch 45 becomes en ga ed and the core member 4? rotates with the plate 45 and shaft 44. A. compression coil spring 555 disengages the clutch d5 when the coil 53 is dcenergized.

The core member ii of clutch 45 has a lug 54 at"- tached thereto. Pivoted to this lug is a link. 55, which in turn is pivoted to the arm 25 of governor 23. The core member M of clutch 45, upon partial rotation through the plate 16 on shaft 44, serves to turn the arm 25 and the shaft 24 in the desired direction. thereby varying the speed of the prime mover ill.

The freonency--1natching device l9 includes a core structure 82 comprising two separate core members 63 and 64. Both of these core members are U-shaped in form and are provided with spaced parallel legs 65, 66, 61 and 63. These core nbers are mounted on a base E9 by means of iollcwi construction. Overlying the said base are lls ll of insulating material on which the legs $35 and ill of the core members 63 and rest. Bolts l2 extend jointly through the base (ill, the block l'l and legs of said core member, and hold said core members in spaced relation with respect to the base 89. It will be noted that the en s of the legs 65, rill, 3'5 and 68 of the core members 5-3 and 64 form magnetic poles which have pole faces 75, i6, 1'! and 78, all lying in a common plane. Mounted on the legs 65 and 68 of the core members 63 and 64 are windings I3 and M.

Operating in conjunction with the core struc ture is an armature "59 provided with two spaced core members BI and B2. The armature l9 co sists of a U-shaped frame member 83 between which the core members BI and 82 are disposed. Rive-ts 84, extending through said frame member and core members, rigidly secure the same togethe-r. The armature I9 is mounted for swinging movement on an arbor 85 which is attached to an adjustable support 86. Bearing screws 81 and 88 are threaded into the frame member 83 and held in adjusted position relative thereto by means of lock nuts 89. These bearing screws have conical bearing cavities BI formed therein which engage conical ends 92 formed on the arbor 85. By means of this construction, the armature I9 mounted to swing freely relative to the core structure Q2. The support 85 is provided with. a threaded shank 93 extending outwardly there-- from. This shank passes through a block 94 of insulating material which is attached to the base 69 by means of bolts 95 and 9G. Nuts 91 and 9B. threaded on the shank 93, hold the adjustable support 86 in adjusted position.

The armature I9 has attached to it a strip of insulating material which has mounted on it two movable contacts IDI and H32. Both of these contacts are connected together by means of a conductor IE3 supported on the insulating strip 99. The contacts IflI and H12 are adapted to engage either of two fixed contacts ltd and I05 which are supported on posts I05 and i8"! issuing outwardly from the base 89. These various contacts form two switches indicated in their entirety by the reference numerals Hi8 and I99. A flexible connection ill is connected to the conductor I03 to a binding post I I2 mounted on the base 59. The contacts I64 and I05 are mounted on screws iii-l which are threaded into the posts Hi6 and Hill which are held in position by of lock. nuts Hi.

The line switch 22 previously referred to is of ordinary construction and comprises a winding IE5 with respect to which a core member H6 is movable. The core member Iiti carries a shaft ill of insulating material and on WiliCh are mounted three switch bars H8, I I9 and I2I. The switch bar [I8 is normally in engagement with two fixed contacts i122 and 123 which iorrn a normally-closed switch H4. The switch bar H9 is normally spaced from but adapted upon energizer-- tion to engage two fixed contacts I25 and RE which form a normallympen switch I21. In a similar manner, the switch bar I2! is normally spaced from but is adapted to engage upon energization two fixed contacts I28 and (28 which form a normally-open switch I3I.

In conjunction with the frequency-matching device, the synchronizing device 2|, previously referred to, is employed and serves to connect the generator II to the system line 20 when the frequency, voltage and phase of the generator the are proper. Inasmuch as the invention will operate with any of the well known forms of synchronizing devices, the construction of the synchronizing device 2I has not been shown in detail. For the purpose of illustrating a synchronizing device, such as disclosed in the patent to Edwin Swanson, Patent No. 2,089,448, issued on the th day of August, 1937, has been shown. Preferably, this device comprises a core structure I32 having two windings I33 and I34 thereon. An armature I35 cooperates with poles I36 and I3I formed on the core structure I32. This armature carries a movable contact I38 adapted to engage a fixed contact I39 which forms a switch indicated in its entirety by the reference numeral MI.

The switches I21 and I3I of the line switch 22 constitute the main switches and are normally open. These two switches are connected in the generator line 30, the conductor I4 of the line 30 being connected to the contacts I25 and I26 and the conductor I5 being connected to the contacts I28 and I29. When th switch I22 is open, the generator II is disconnected from the alternating-current system of which the line 28 is a portion.

The frequency-matching device I 3 is connected in the frequency-matching system in the following manner: The winding I3 is connected by means of a conductor I42 to the conductor I2 of th system line 20. The other end of this winding is connected by means of a conductor I43 to a condenser I44 which, in turn, is connected by means of a conductor I45 to the other conductor I3 of the line 20. The winding I4 is connected by means of a conductor I46 to the contact I22 of switch I24, while the other contact I23 of said switch is connected by means of a conductor I41 to the conductor I5 of the generator line 30. The other end of the winding I4 is connected by means of a conductor I48 to a condenser I49 which, in turn, is connected by means of a conductor I5I to the other conductor I4 of the generator line 30. It will thus be seen that the two windings I3 and I4 are separately energized, one from the system line and the other from the generator line 30. In practice, suitable condensers I44 and I49 are employed, so that the circuits containing the windings 13 and I4 become resonant at a frequency somewhat above normal frequency.

The motor I1 is connected as follows: One end of winding 36 is connected by means of a conductor I52 to the conductor I46 previously referred to. The other end of this winding is connected by means of a conductor I53 directly to the conductor I4 of line 30. The two windings 38 and 39 of the motor are connected in series by means of a conductor I54 which is connected to one end of each of said windings, In a similar manner, the windings 31 and M are likewise connected in series by means of a conductor I55 which is connected to one end of each of said windings. The other end of each of the windings 31 and 38 is connected together by means of a conductor I56 which, in turn, is connected by means of a conductor I5I to the flexible connection III which, in turn, is connected to the conductor I03 of the frequency-matching device I9. The other end of the winding 39 is connected by means of a conductor I58 to the contact I04 of switch I08. In a similar manner, the other end of the winding M is connected by means of a conductor I 59 to the contact I05 of switch I09. It will thus be readily comprehended that when the line switch 22 is deenergized, switch I24 is closed and the main winding 36 of the motor I1 is energized whenever generator voltage is available. It will further be comprehended that the direction of rotation of said m0- tor depends upon which of the switches I08 or I09 is closed.

The winding I33 of the synchronizing device 2I is connected on one end by means of a conductor ISI to the conductor I3 of line 20. The other end of this winding is connected by means of a conductor I62 to the conductor I42 which, in turn, is connected to the other conductor I2 of line 23. The windings I3 and I4 of the frequency-rnatching device I9 are connected together by a conductor I63 which, in turn, is connected by means of a conductor I 54 with one end of the winding I34 of the synchronizing device 2|. The other end of winding I34 is connected by means of a conductor I65 to the contact I39 of switch MI and is further connected by means of a conductor I 66 with the conductor I5I, being thus energized from the line 30. The contact I 38 of the synchronizing device 2| is connected through its armature with a conductor I 5! which, in turn, is connected to the winding I I5 of the line switch 22. ihe other end of the winding I I5 0f the said iine switch is connected to a conductor I68 which, in turn, is connected to the conductor I41 and is thus energized from the lin 30 through the switch MI.

The winding 53 of the magnetic clutch 45 is connected on one end to a conductor I69 which, in turn, is connected to the conductor I53, being thus connected to the conductor I4 of line 30. The other end of the winding 53 is connected by means of a conductor I 1| to the conductor I52 which, in turn, is connected to the contact I 22 of switch I24. In this manner, the clutch 45 is energized from the line 30.

My invention operates in the following manner: In normal position, the line switch 22 is deenergized and the switches I27 and I3I are open while the switch I 24 is closed. At the same time, the switch I M of the synchronizing device 2i is open. Since the energization of the winding I4 comes from the line 30, said winding, at the time of starting the generator, is deenergized, while the winding 43, being connected to the line 20, is fully energized. This causes the core member iii of armature I9 to be attracted, whereby the switch I08 is open and the switch I09 is closed. If the generator I I is deenergized, motor II remains inoperative, due to the fact that the main winding 36 thereof is energized from the line 36. Also, clutch member 4? remains stationary due to the fact that clutch 43 being connected to line 33 is deenergized. Since the switch I09 is closed, windings M and 31 become short-circuited and act as shaded-pole windings which give the motor torque in one direction of rotation. If, now, the prime mover. I6 is started up, generator I I commences to build up voltage and to increase the frequency of the same. During such period, the motor I! becomes energized and commences to rotate and, in turn, rotates shaft 44. At the same time, clutch 45 becomes energized and the clutch member 4'! turns and moves the link 55 and the arm 25 in a counter-clockwise direction, as shown in Fig. 2. This has the effect of opening the throttle and causing the prime mover I6 to increase its speed. As the generator II reaches synchronizing speed, the two magnetic circuits energized by the windings I3 and I4 become balanced and the two switches I08 and I09 both open. This causes the motor I1 to stop. If all the electrical conditions in the system are proper, the synchronizing device 2| will then close the switch MI and energize the coil H of line switch 22 which closes the switches I21 and I3I and connects the line 30 to the line 20. If, however, conditions are not proper, the frequency of the generator will exceed that of the line and cause the magnetic circuit through the core member 68 to attract the core member 82 of armature 19 with greater force than the attraction on the core member BI, thereby closing the switch I08 and maintaining the switch I09 open. This short-circuits the other windings 38 and 39 of the motor I1 and causes said motor to rotate in the opposite direction. Arm 25 in shaft 24 of the governor 23 is now moved in the opposite direction and the speed of the prime mover is reduced. This continues back and forth until such a time as all of the electrical conditions of the electric generator are proper for connecting the generator to the electric system, which is then accomplished by means of the synchronizing device 2% in the customary manner. Upon operation of the synchronizing device 2|, line switch 22 operates to close the switches I21 and I3I and, at the time, to open the switch I24. The opening of this switch deenergizes the motor I! and also the magnetic clutch 45, so that the member 41 is free to rotate on shaft 44. The governor 23 may now operate independently of the motor H to control the speed of the prime mover I6 and to maintain the desired speed for the same.

I have found that where the condensers I44 and I49 are so selected that resonance in the two circuits containing the windings I3 and M occurs approximately 25% above normal frequency that excellent results are produced. At the same time, the armature i9 is raised sufiiciently to form substantial air gaps between the core members BI and 82 and the pole faces I5, I6, I1 and I8. This gives a straight line variation in the magnetomotive forces in the magnetic circuits, whereby uniformity of action of the device is procured. The movement of the armature I9 is limited by means of contacts IE4 and I05, so that the core members 8! and 82 can not reach the said pole faces and cause sticking of the armature to these pole faces.

The advantages of the invention are manifest. The frequency-matching device is simple in construction and can be built at a nominal expense. This device will operate in conjunction with any type of synchronizing apparatus. By means of the normally-closed switch operated by the line switch, the entire system is cut out after the generator line has been connected to the system line. Also, the driving means for varying the speed of the prime mover is disconnected so that the entire freqency-matching device is inactive until the generator has again become disconnected from the electric system. Thi allows the generator to operate in its customary and intended purposes without interference from the frequency-matching device.

Changes in the specific form of my invention, as herein described, may be made within the scope of what i claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. In a synchronizing system for connecting to an electrical system a generator driven by a prime mover having a speed-varying device, said device being provided with a movable operating member and yieldable means for normally operating the same, an electric motor for moving said operating member independently of the yieldable means, a clutch between said motor and operating member, a frequency-matching device for actuating said motor, means for connecting the generator to the system and means operable upon connection of the generator to the electrical system for disengaging said clutch to release said operating member and subject the speed-varying device to the action of the yieldable means.

2. In a synchronizing system for connecting to an electrical system a generator driven by a prime mover having a speed-varying device, said device being provided with a movable operating member and yieldable means for normally operating the same, motive means for moving said operating member independently of the yieldable means, driving means between said motor and operating member, a frequency-matching device for actuating said motive means, means for connecting the generator to the system and means operable upon connection of the generator to the electrical system for rendering said driving means inoperative and subject the speed-varying device to the action of the yieldable means.

3. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure providing two magnetic circuits, a winding associated with the core structure and producing magnetic flux in one of the magnetic circuits, said winding being energized solely by the system, a second windin associated with the core structure and producing magnetic flux in the other magnetic circuit, said second winding being energized solely by the generator, a movable armature associated with the core structure, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the opposite direction by the flux produced by the other of said windings, a control circuit and switch means therein operated by said armature.

4. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure providing two magnetic circuits, a winding associated with the core structure and producing magnet flux in one of the magnetic circuits, said winding being energized solely by the system, a second winding associated with the core structure and producing magnetic flux in the other magnetic circuit, said second winding being energized solely by the generator, a movable armature associated with the core structure and movable in opposite directions, and control means actuated by said armature and operable upon movement of said armature in one direction to increase the frequency of said generator and in the other direction to decrease the frequency of the generator.

5. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, two separate core members providing independent magnetic circuits, a winding on one of said core members energized solely by the electrical system, a winding on the other of said core members energized solely by the generator, a movable armature having parts associated with each of said core members and forming therewith air gaps, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the oppo- 9 site direction by the flux produced by the other of said windings, a control circuit and switch means therein operated by said armature.

6. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure providing two magnetic circuits, a winding associated with the core structure and producing magnetic flux in one of said magnetic circuits, an electrical circuit energized from the system and including said winding, a condenser in said electrical circuit connected in resonant relationship with respect to said winding, 21, second winding associated with the core structure and producing magnetic flux in the other magnetic circuit, a, second electrical circuit including the second winding and energized by the generator, a condenser in said second electrical circuit connected in resonant relationship with respect to said second winding, a movable armature associated with the core structure, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the opposite direction by the flux produced by the other winding, a control circuit, and switch means therein operated by said armature.

7. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure providing two magnetic circuits, a winding associated with the core structure and producing magnetic flux in one of said magnetic circuits, an electric circuit energized from the system and including said winding, a condenser connected in said circuit in series with said winding, a second winding associated with the core structure and producing magnetic flux in the other magnetic circuit, a second electrical circuit including the second winding and energized by the generator, a condenser connected in said second circuit in series with said second winding, a movable armature associated with the core structure, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the opposite direction by the flux produced by "the other winding, a control circuit, and switch means therein operated by said armature.

8. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, two separate core members providing independent magnetic circuits, a winding on one of said core members energized solely by the electrical system, a winding on the other of said core members energized solely by the generator, a movable armature having parts associated with each of said core members and forming therewith air gaps, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the opposite direction by the fiux produced by the other of said windings, limit means for controlling the movement of the armature to limit the lengths of the air gaps to predetermined minimums.

9. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two magnetic poles, a winding nergized by the system and producing magnetic flux through one of said poles, a winding energized by the generator and producing magnetic flux through the other of said poles, an armature having portions disposed adjacent 10 said poles and forming air gaps therebetween, supporting means for supporting said armature for movement toward and from the poles so that one of the portions of said armature approaches' its pole and the other portion recedes from its pole when the armature is moved in one direction and adjustable guide means for guiding said supporting means for movement toward and from the poles to simultaneously decrease or increase the lengths of said air gaps, a control circuit and switch means therein operated by said armature.

10. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two magnetic poles, a winding energized by the system and producing magnetic flux through one of said poles, a winding energized by the generator and producing magnetic flux through the other of said poles, an armature having portions disposed adjacent said poles and forming air gaps therebetween, means for supporting said armature for movement toward and from the poles to alternately vary said air gaps, adjustable guide means for guiding the armature for movement toward and from the poles to simultaneously decrease or increase said air gaps, a control circuit and switch means therein operated by said armature.

11. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two magnetic poles, a winding energized by the system and prod cing magnetic fiux through one of said poles, a winding energized by the generator and producing magnetic flux through the other of said poles, an armature having magnetic portions disposed adjacent said poles and forming air gaps therebetween, pivot means for pivoting said armature for swinging movement in opposite directions to cause one of said air gaps to increase and the other to decrease upon movement of the armature in one direction, means for guiding said pivot means for movement to cause both of said air gaps to simultaneously decrease or increase, a control circuit and switch means therein operated by said armature.

12. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two poles formed with pole faces disposed in a common plane, a winding energized by the system and producing magnetic flux through one of said poles, a winding energized by the generator and producing magnetic flux through the other of said poles, an armature having magnetic portions disposed adjacent said poles and forming air gaps therebetween, pivot means for pivoting said arma ture for swinging movement in opposite directions to cause one of said air gaps to increase and the other to decrease upon movement of the armature in one direction, means for guiding said pivot means for movement toward and from the plane of said pole faces, a control circuit and switch means therein operated by said armature.

13. In a irequency matching device for Varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure providing two magnetic circuits, a winding associated with the core structure and producing magnetic flux in one of said magnetic circuits, an electrical circuit energized fr m the system and including said winding, a

condenser in said electrical circuit connected in resonant relationship with respect to said winding, a second winding associated with the core structure and producing magnetic flux in the other magnetic circuit, a second electrical circuit including the second winding and energized by the generator, a condenser in said second electrical circuit connected in resonant relationship with respect to said second winding, a movable armature associated with the core structure, said armature being urged to move in one direction by the flux produced by one of said windings and being urged to move in the opposite direction by the flux produced by the other winding, said condensers and windings being proportioned to produce resonance in both of said circuits at approximately 125% of the normal frequency of the electrical system, a control circuit, and switch means therein operated by said armature.

14. In a synchronizing system for connecting to an electrical system a generator driven by a prime mover having a speed-varying device, said device being provided with a movable operating member and yie1dable means for normally operating the same, an electric motor for moving said operating member independently of the yie1dable means, an electric clutch adapted upon energization to effect a drive between said motor and operating member, a frequency-matching device for actuating said motor, a line switch for connecting the generator to the system and a switch normally closed when said line switch is open for controlling the energization of said clutch, said switch being adapted to be opened upon closing of the line switch.

15. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two magnetic poles, a winding energized by the system and producing magnetic flux through one of said poles, a Winding energized by the generator and producing magnetic flux through the other of said poles, an armature having portions disposed adjacent said poles and forming air gaps therebetween, means for supporting said armature for movement toward and from the poles to alternately vary said air gaps, adjustable guide means for guiding the armature for movement toward and from the poles to simultaneously decrease or increase said air gaps, an adjusting member acting between said armature and said guide means for moving said armature relative thereto, a control circuit and switch means therein operated by said armature.

16. In a frequency-matching device for varying the frequency of an alternating-current generator to be connected to an alternating-current system, a core structure having two magnetic poles, a winding energized by the system and producing magnetic flux through one of said poles, a winding energized by the generator and producing magnetic flux through the other of said poles, an armature having portions disposed adjacent said poles and forming air gaps therebetween, means for supporting said armature for movement toward and from the poles to alternatively vary said air gaps, adjustable guide means for guiding the armature for movement toward and from the poles to simultaneously decrease or increase said air gaps; a threaded member acting between said armature and said guide means for moving said armature relative thereto, a control circuit and switch means therein operated by said armature.

WILLIAM R. CARTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,091,141 Zingg Sept. 28, 1937 2,104,801 Hansell Jan. 11, 1938 FOREIGN PATENTS Number Country Date 29,639 Netherlands Apr. 15, 1933 

